Trimmer condenser



Sept. 11, 1956 M. w. SLATE 2,762,958

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23 22 4 Q T I 26 3H?! 27 ,28 3| L .l I37 8% INVENTOR. 4 MATTHEW w. SLATE A TTORNEYS United States Patent 9 2,762,958 TRIMMER @GNDENSER Matthew W. Slate, New York, N. K, assignor to Allen B. Du Mont Laboratories, Inc, Clifton, N. J., a corporation of Deiaware Application December 22, 1952, Seriai 327,241 3 Ciairns, (Cl. 317-249) This invention relates to electrical tuned circuits and in particular to a novel trimmer condenser.

An object of the invention is to rovide trii liner condenser which is physically compact and inexpensive to manufacture.

Another object is to provide a trimmer condenser particularly adapted for use in switch type or turret tuners, having a. low value of inherent inductance, and having as a portion thereof an electrical contact terminal.

Referring to the drawings,

Figure 1 is a side View of a preferred embodiment of the invention;

Figure 2 is a top view of Figure 1;

Fig. 3 is a partial schematic and partial symbolic representation of a tuning system employing several of the novel trimmer condensers in series-tuned circuits; and

Figure 4 represents the novel condensers used in parallei-tuned circuits.

Referring now to the drawings there is shown at 11 an insulative support which has a screw 12 passing therethrough and securely attached thereto. The head 13 of the screw is preferably rounded and is positioned against a side of the support member 11, and provides a switch-type electrical contact as will be described. An insulative cylinder 14 having an internal axial thread, is threaded onto the screw 12. A conductive band 16 is positioned on the surface of the cylinder 14. Preferably this conductive band is made of copper or silver or the like, and the supporting cylinder 14 is made of ceramic material. A transverse slot 17 or the like is provided at an end of the supporting cylinder 14 for purposes of turning by means of a screw driver or the like.

A resilient contact am 1.55 is attached to the support member 11 at an end 19 thereof, whereas the remaining end 20 thereof is preferably rounded as shown, and makes resilient sliding engagement with the conductive band 16. The end 19 of the resilient arm 18 is one terminal of the trimmer condenser, whereas the rounded contact head 13 of the screw 12 is the other terminal of the trimmer condenser. The end 19 of the contact arm 18 may be attached to the member 11 by means of a rivet 21 passing through the member 11 and having a contact head 22.

in the use for which the condenser is particularly contemplated, the support member 11 will be a movable switch plate or a tuning strip in a turret type electrical tuner. A fixed electrical contact arm 23 is fixedly attached to an electrical circuit unit 24, and is positioned so as to selectively make electrical contact with the contact terminal 13 when the terminal 13 is moved into a suitable position. Another contact arm 23a may be attached to circuits 24a and positioned to selectively engage the contact head 22 of the rivet 21.

In Figure 3, a dotted enclosure 26 represents a turret type electrical tuner or other type of switch tuner containing a plurality of tuned circuits 27, 28 and 29, each comprising an inductance connected in series with a novel trimmer condenser 31, 31', 31" of the type shown in Figures 1 and 2. A plurality of electrical contact terminals 13, 13' and 13" extend from the trimmer condensers 31, 31' and 31" in the unit 26. When the unit 26 is moved in the directions shown by the arrow, the contact terminals of the trimmer condensers selectively make electrical engagement with the fixed contact arm 23.

In Figure 4 parallel-tuned circuits are employed which are connected selectively to the contact arms 23, 23a through the contacts 13, 22 and i3, 22.

The novel trimmer condenser is adjusted by turning the cylinder 14, whereupon this cylinder moves axially with respect to the end 32 of the screw 12. This varies the capacitance between the conductive band 16 and the screw 12, since the end 32 of the screw 12 is within the confines of the band 26, as shown in Figure 1.

It will be appreciated that the invention accomplishes a combination of a trimmer condenser and a contact terminal which is physically compact and inexpensive to manufacture and which is electrically efiicient due to the short electrical leads involved.

While a preferred embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that certain modifications thereof may be made within the spirit and scope of the invention. The scope of the invention is defined in the following claims.

What is claimed is:

1. An assembly comprising an elongated electrically conductive threaded member having an electrical contact at an end thereof, a rotatable insulative cylinder containing an axially threaded opening, said cylinder being threaded by means of said opening partially on said threaded member at the end opposite said contact, electrically conductive material positioned on the outer surface of said cylinder, and a resilient contact arm positioned to make slidablc engagement with said conductive material whereby when said rotatable cylinder is rotated on said threaded member the capacitance between said threaded member and said conductive material is varied.

2. A condenser assembly comprising an insulative support member, an opening through said member, an elongated electrically conductive member passing through said opening and having an electrical contact head at one side of said support member and being threaded at the other side of said support member, a rotatable cylinder of insulative material having its one end slotted and its other end threaded partly onto the threaded end of said elongated member, electrically conductive material positioned on the outer surface of said cylinder, and a resilient contact arm positioned on said support member and making engagement with said conductive material whereby when said rotatable cylinder is rotated on said conductive member the capacitance between said contact head and said contact arm is varied.

3. The condenser assembly in accordance with claim 2, in which said contact arm is attached to said support member by means of a rivet passing through said support member, said rivet having an electrical contact head on the same side of said support member as is said firstmentioned contact head.

References Cited in the file of this patent UNITED STATES PATENTS 1,632,130 Haddock June 14, 1927 2,250,366 Frisbee July 22, 1941 2,305,355 Lips et al Dec. 15, 1942 2,390,009 Stott Nov. 27, 1945 2,504,758 Thias Apr. 18, 1950 2,545,681 Zepp et al. Mar. 20, 1951 2,670,453 Leuthold Feb. 23, 1954 FOREIGN PATENTS 584,251 France Nov. 17, 1924 420,055 Great Britain Nov. 23, 1934 523,869 Great Britain July 24, 1940 592,501 Great Britain Sept. 9, 1947 

